QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940060.txt

Internet Message Format | 1994-11-13 | 17KB

Date: Thu, 10 Mar 94 04:30:18 PST
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
Errors-To: [e-mail]
Reply-To: [e-mail]
Precedence: Bulk
Subject: Ham-Ant Digest V94 #60
To: Ham-Ant


Ham-Ant Digest              Thu, 10 Mar 94       Volume 94 : Issue   60

Today's Topics:
                         Commercial Antennas
                      Dipole or Vertical for DX?
                     GAP Challenger VIII (2 msgs)
                    Help: Antenna for FAX on boat
                  LUMINA APV, mobile antenna - HELP
                             MFJ-245 SWR
                MFJ 1798 80-2 Meter Vertical (2 msgs)
                 Question about mobile antenna 40/80m
                RG-58 and Discone ant. problem at VHF
                            test (5 msgs)
                            testing 1,2,3
            Thick Ethernet as Transmission Line? (2 msgs)

Send Replies or notes for publication to: <[e-mail]>
Send subscription requests to: <[e-mail]>
Problems you can't solve otherwise to [e-mail].

Archives of past issues of the Ham-Ant Digest are available
(by FTP only) from UCSD.Edu in directory "mailarchives/ham-ant".

We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party.  Your mileage may vary.  So there.
----------------------------------------------------------------------

Date: 9 Mar 94 19:38:10 GMT
From: agate!howland.reston.ans.net!cs.utexas.edu!swrinde!sgiblab!rtech!ingres![e-mail]
Subject: Commercial Antennas
To: [e-mail]

Anyone have a source for commercial antennas?

Specifically looking for a colinear vertical cut near the 144 MHz band
with good gain for a repeater.  Durability is most important and then
the ability to tune the lobes (have the antenna cut accordingly).

Thanks in advance.

Post here, or email to:

[e-mail]
Kerry Kurasaki

------------------------------

Date: 8 Mar 94 18:44:40 GMT
From: agate!howland.reston.ans.net!news.intercon.com!udel!news.sprintlink.net!direct!news.direct.net![e-mail]
Subject: Dipole or Vertical for DX?
To: [e-mail]

[e-mail] wrote:
:     Just wanted to know if a dipole or vertical performs better for QRP DX?
:     This is on 20 meters.  73 de 9V Daniel

Hi Daniel, My rotatable dipole at 60 ft. always outperforms my 17m vertical.
The 17m vertical is a modified CB antenna with the base at 20 ft with 4
radials and is fed with coax. The rotatable dipole is fed with ladder-
line and I use it on all bands 20-10m. No report has been in favor of the
vertical over the dipole.

73, Cecil, [e-mail]

------------------------------

Date: Wed, 9 Mar 1994 19:46:30 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!vixen.cso.uiuc.edu!howland.reston.ans.net!news.intercon.com!news.pipeline.com!malgudi.oar.net!utnetw.utoledo.edu!uoft02.utoledo.edu![e-mail]
Subject: GAP Challenger VIII
To: [e-mail]

Anybody got experience with the GAP Challenger VIII. As I only have room for
one antenna, the many bands on it looks good.  I am concerned about mounting
it on a roof.  The antenna lists at 31.5 feet, and my roof is 26 feet up.
Anybody tried it, or done something similiar??

------------------------------

Date: 10 Mar 94 03:46:26 GMT
From: agate!howland.reston.ans.net!sol.ctr.columbia.edu!news.mtu.edu!news.mtu.edu![e-mail]
Subject: GAP Challenger VIII
To: [e-mail]

[e-mail] wrote:
: Anybody got experience with the GAP Challenger VIII. As I only have room for
: one antenna, the many bands on it looks good.  I am concerned about mounting
: it on a roof.  The antenna lists at 31.5 feet, and my roof is 26 feet up.
: Anybody tried it, or done something similiar??
:I have a GAP DX Challenger VI, and I havent had good luck with it AT ALL!
If you have enough room for a dipole, or sloper, you'll probably be better
off. Much cheaper too!


------------------------------

Date: 8 Mar 94 22:57:13 GMT
From: agate!howland.reston.ans.net!cs.utexas.edu!swrinde!menudo.uh.edu!hounix!mwk![e-mail]
Subject: Help: Antenna for FAX on boat
To: [e-mail]

I would like to install an antenna up on my 30 ft boat for receiving weather fax
transmissions (5-15 MHz, I think is the general range).

I think my only options are whip or random wire.  I can mount a reasonably
sized whip pretty easily.  A random wire can be strung (nearly vertical)
parallel to the backstay; some people use their backstay, but load bearing
isolators are expensive.  I don't think I can rig a dipole without enterfering
with the sail plan.

Please advise what configuration would work best.

I've seen some outfit selling a combination of 8ft whip (CB antenna I guess)
with an MFJ random wire tunner.

I'll be trying to connect this to my Sangean 803A, which has an RCA input for
external antenna - I've heard that crocodile clipping to the telescopic antenna
is sometimes better than using the external antenna jack - why is that?

Please advise whether any type of impedance matcher/amplifyier will do me any
good.

Thanks,
    Jeremy.
--
Jeremy Waters
[e-mail]

------------------------------

Date: Wed, 9 Mar 1994 19:26:39 GMT
From: agate!howland.reston.ans.net!cs.utexas.edu!utnut!torn!uunet.ca!uunet.ca!dmog10.bell.ca!bcocek!vega![e-mail]
Subject: LUMINA APV, mobile antenna - HELP
To: [e-mail]

Does anyone have a suggestion for mobile antenna to put on a Chevrolet
LUMINA APV? This vehicule is PLASTIC...

What are your experience or suggestion with that kind of problem!

Thanks,


Yvan - VE2YDU

Bell SYGMA, Telecom Solutions
30 Renaud, Loretteville (Qc) CANADA  G2A 2K7
TEL: [phone]          FAX: [phone]
Internet: [e-mail]     HAM: VE2YDU@VE2GPQ.#QBC.PQ.CAN.NA
-----------------------------------------------------------------------
Disclaimer: The opinions expressed here are mine and not my employer's.

------------------------------

Date: Wed, 9 Mar 1994 15:49:29 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!gatech!swrinde!sgiblab!cs.uoregon.edu!reuter.cse.ogi.edu!hp-cv!hp-pcd!hpcvsnz![e-mail]
Subject: MFJ-245 SWR
To: [e-mail]

Fred McKenzie ([e-mail]) wrote:
: In article <2lh939$[e-mail]>, [e-mail]
: (Wayne Price) wrote:
: >    Lowest SWR occurs at resonance.

: Wayne-

: I'm curious.  Are you sure this is true?

: If you had a resonant 72 Ohm dipole with 50 Ohm cable, it could be
: represented as a 1.44:1 circle on a Smith Chart.  Does the complex
: impedance of the dipole go outside the circle as you move away from
: resonance, or does it make a pass inside first?

Resonance can be defined as a point at which the reactive component
of the impedance is zero.  If you change that reactive component, you
move exactly tangent to the circle you mention, and at that point,
the d(SWR)/dX is zero--you get no SWR change for a delta reactance
change.  Yes, the reactance causes motion on a circle, but that
circle and the SWR circle are tangent at that resonance point.

BUT (and don't anyone dare take that preceeding paragraph out of
this context) the RESISTIVE component is ALSO changing as you
change frequency (or antenna length, equivalently).  As a result,
there is a d(SWR)/dR component that is NOT zero, and it will
_always_ get you to an incrementally lower SWR in one direction
or another.  For the case you mentioned, it will be at a frequency
slightly lower than resonance.

Finally, this is an incremental thing.  Don't expect to be very far
from resonance when the SWR is lowest in such a case.

Also, this assumes a resistive component that changes with frequency.
This is the case for a 1/2 wave center-fed dipole, or a 1/4 wave fed
over ground, but for an end-fed 1/2 wave, or a 3/4 wave, or any
resonances above that first one, the dR/df is likely to be extremely
close to zero.

73, K7ITM

------------------------------

Date: 8 Mar 94 14:45:28 GMT
From: agate!howland.reston.ans.net!math.ohio-state.edu!news.acns.nwu.edu!ftpbox!mothost!delphinium.cig.mot.com!rtsg.mot.com![e-mail]
Subject: MFJ 1798 80-2 Meter Vertical
To: [e-mail]

Has anyone out there obtained and tried out the new MFJ 1798 80 thru 2 Meter
Vertical antenna yet?  If so any comments on performance, VSWR, BW, Mechanical contruction, etc.

Replies to group or direct.  Thanks

--
     ======================================================================
     | Charles H. Reichert    708-632-6669 Work - MOTOROLA, INC  Cellular |
     | KD9JQ                  708-358-3827 HOME - after 8PM CST  weekdays |
     | [e-mail]   955 Concord Ln.  Hoffman Ests., IL. 60195   |
     ======================================================================

------------------------------

Date: Wed, 09 Mar 1994 10:13:14 -0500
From: titan.ksc.nasa.gov!k4dii.ksc.nasa.gov![e-mail]
Subject: MFJ 1798 80-2 Meter Vertical
To: [e-mail]

In article <2li328$[e-mail]>, [e-mail]
(Charles H. Reichert) wrote:
> Has anyone out there obtained and tried out the new MFJ 1798 80 thru 2 Meter
> Vertical antenna yet?  If so any comments on performance, VSWR, BW, Mechanical contruction, etc.

Charles-

I don't find the MFJ 1798, in the Amateur Electronic Supply catalog, which
has been out for about 4 months.  They do have the 1796 listed, which is 40
thru 2 Meters.  Since the MFJ 1796 was listed in the catalogs for about a
year before it made it to production, I wouldn't expect to see a production
model 1798, for quite some time.

MFJ seems to have a problem in this area.  They may be "testing the
market", by announcing products that are not yet in production.  If no one
orders them, they may never make it to production.

Have you heard anything good about the MFJ 1796, 40 thru 2 Meter model?  I
get the impression that it works, but is somewhat fragile.

73, Fred, K4DII

------------------------------

Date: Wed, 09 Mar 1994 10:44:08 -0500
From: titan.ksc.nasa.gov!k4dii.ksc.nasa.gov![e-mail]
Subject: Question about mobile antenna 40/80m
To: [e-mail]

In article <[e-mail]>, [e-mail] (Cecil Moore)
wrote:
> Hi Manne, Maxwell, author of "Reflections" doesn't think much of
> Hustlers. They are lossy, low-Q, and near self-resonance... all
> to "lower the SWR for the wrong reasons." Maxwell says that, in
> general, the mobile antenna with the highest SWR will radiate the
> most power. Hamsticks from Lakeview are good hi-Q mobile antennas.
> I've heard the Texas BugCatcher is pretty good although Maxwell says

Cecil-

I am having good results with Hustler low-power resonators, with the mast
that folds low (fender mount), but using a magnet mount on the roof of my
car.  I have made contacts on 75 meter SSB, but not enough to judge by.
However, results on 40 meters have been very good.  Some of the other
antennas you mentioned may be better, but I doubt by much.  Also, I doubt I
could mount a "BugCatcher" on the magnet mount!

I disagree with your assessment of the Lakeview HamStick.  I have one for
75 meters.  I find it has LOWER Q than the 75 meter Hustler (low power
resonator).  By inspection, you can see that the coil is spread over a
greater length of the HamStick, starting lower on the antenna than the
resonator of the Hustler.  Since most of the radiation from such a vertical
antenna comes from the bottom (high current) section, more will be wasted
in the coil wire of the HamStick, than in the mast of the Hustler below the
resonator.  Note:  The 75 meter HamStick has wider bandwidth than the 75
meter Hustler.  Wider bandwidth = Lower Q.

If this disagrees with your reference source, I think there is reason to
doubt your source's credibility.

73, Fred, K4DII

------------------------------

Date: Wed, 9 Mar 1994 18:26:38 GMT
From: envoy![e-mail]
Subject: RG-58 and Discone ant. problem at VHF
To: [e-mail]

Very interesting.  I have had very similar experience with a Radio Shack
discone that was given to me.  I assumed that it was just defective, hence
the gift.  It did seem to perform ok on transmit however (2 mtr FM) which
seemed a bit odd.  I would be interested in others experience and
suggestions as well.

-------------------------------------------------------------------------------
 Jim Mueller      | Work : [phone] | net: [e-mail]
 11865 Deodar Way | Home : [phone] | WB7AUE
 Reno, NV  89506  |                       |


--
-------------------------------------------------------------------------------
 Jim Mueller      | Work : [phone] | net: [e-mail]
 11865 Deodar Way | Home : [phone] | WB7AUE
 Reno, NV  89506  |                       |

------------------------------

Date: 8 Mar 94 17:13:27 GMT
From: dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!oakhill![e-mail]
Subject: test
To: [e-mail]

testing

------------------------------

Date: 8 Mar 94 20:17:47 GMT
From: dog.ee.lbl.gov!ihnp4.ucsd.edu!swrinde!cs.utexas.edu!oakhill![e-mail]
Subject: test
To: [e-mail]

test

------------------------------

Date: 8 Mar 94 20:42:52 GMT
From: dog.ee.lbl.gov!ihnp4.ucsd.edu!swrinde!cs.utexas.edu!oakhill![e-mail]
Subject: test
To: [e-mail]

testing

------------------------------

Date: 8 Mar 94 23:25:06 GMT
From: dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!oakhill![e-mail]
Subject: test
To: [e-mail]

test

------------------------------

Date: Wed, 9 Mar 1994 21:02:43 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!sgiblab!gatekeeper.us.oracle.com!barrnet.net!netnews.synoptics.com![e-mail]
Subject: test
To: [e-mail]

Just like school .   I havent been studying for these damn tests :)

Dave

------------------------------

Date: 9 Mar 94 23:06:46 GMT
From: dog.ee.lbl.gov!ihnp4.ucsd.edu!swrinde!cs.utexas.edu!oakhill![e-mail]
Subject: testing 1,2,3
To: [e-mail]

Test

------------------------------

Date: 8 Mar 94 17:49:42 GMT
From: agate!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!caen!malgudi.oar.net!gomer.aldus.com![e-mail]
Subject: Thick Ethernet as Transmission Line?
To: [e-mail]

I have come across a quantity of Thick Ethernet cable (yellowjacket coax),
Belden YS-21553 style 1478 #1700415-01. Does anyone know whether it is
suitable for use on 2M and 440 MHz? Thanks,


David Mitchell
Aldus Corporation         Bainbridge Ometepe Sister Islands Association
[e-mail]                   [e-mail]

My opinions are my own.

------------------------------

Date: 8 Mar 94 21:44:14 GMT
From: agate!howland.reston.ans.net!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!skopen.dseg.ti.com!sc04![e-mail]
Subject: Thick Ethernet as Transmission Line?
To: [e-mail]

Yes, the thick ethernet coax works great up 400 mhz.  However, examine the coax for
tap holes from the ethernet transceivers--I found the holes can cause considerable
problems with contamination, reflections, gremlins, etc.

Regards,
Jim

------------------------------

Date: Wed, 9 Mar 1994 19:15:01 GMT
From: ihnp4.ucsd.edu!usc!elroy.jpl.nasa.gov!swrinde!gatech!news-feed-1.peachnet.edu!umn.edu!uum1!kksys.com!edgar!moron!nmmc!cgc.NMMC.Com![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>du
Subject : Re: Slim-jim dimensions?

In article <[e-mail]> [e-mail] (Iain Philipps) writes:
>From: [e-mail] (Iain Philipps)
>Subject: Re: Slim-jim dimensions?
>Date: Wed, 9 Mar 1994 08:01:40 +0000
>In article <[e-mail]>
>           [e-mail] "Christopher Cox" writes:
>
>Just to set the record straight :-)
>
>     Fred Judd, G2BCX
>     Practical Wireless, April 1978
>
>See. America is bad for your memory.
>
>--
>Iain Philipps

G8SJP - now there's a call from the past!  Thanks Iain for setting me
straight.

Chris  W0/G4JEC
       ex G8PTC
--
Chris

   Chris Cox  W0/G4JEC                     [e-mail]
   Network Analyst                                NIC Handle:   CC345
   North Memorial Medical Center                  Tel: [phone]
   3300 Oakdale Avenue North                      Fax: [phone]
   Robbinsdale, MN  55422

     ----- For mail of a more social nature, please use -----
           Internet: [e-mail]
           Amprnet:  [e-mail]

------------------------------

End of Ham-Ant Digest V94 #60
******************************